Reading Essentials for Biology Glencoe (794133), страница 83
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Oxygen andcarbon dioxide are exchanged through the tiny blood vessels, or capillaries, in the gill filaments.Gill FilamentsCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What kind of hearts do fishes have?All fishes have two-chambered hearts. Blood that nolonger has oxygen flows into one chamber of the heartfrom the body tissues. The second heart chamber pumpsblood directly to the capillaries located in the fish’s gills.Oxygen is picked up from the water passing over the gills.Carbon dioxide is released.
The oxygen is carried from thegills to the fish’s body tissues. Blood flows through a fish’sbody slowly. The flow of blood is shown in the figure tothe right. Most of the heart’s pumping action is used topush blood through the gills, not through the body tissues.WaterGill FilamentsAortaGillsCapillarynetworkHeartHow do fishes reproduce?All fishes reproduce sexually. The method of reproduction variesfrom one fish species to another.
For most fishes, fertilization anddevelopment of the embryos is external. Eggs and sperm arereleased directly into the water. Some species of fishes leave theireggs and sperm in a more protected area, such as on plants floating in the water. Most fishes produce large numbers of small eggsat one time.
Hagfishes produce small numbers of large eggs.Fishes whose skeletons are made of cartilage have internal fertilization. Skates leave fertilized eggs on the ocean floor. Somefemale sharks and rays carry developing young inside their bodies.These young fishes are well developed when they are born. Thisincreases their chance for survival.Most bony fishes have external fertilization and development.This type of external reproduction is called spawning. Fishes thatspawn, such as cod, may produce as many as 9 million eggs. MostREADING ESSENTIALS2. What form of reproduction is common to allfishes?________________________________________________________________________Chapter 30365NameDateClassSectionFishes, continued________________________of these fishes provide no care for their young after they spawn.Only a few of the young will live to be adults. In some bonyfishes, such as guppies and mollies, fertilization and developmenttake place internally.
Some fishes, such as the mouth-broodingcichlids, stay with their young after they hatch. When young cichlids are threatened by predators, the parent fishes collect theiryoung in their mouths to protect them.________________________What kind of fins do fishes have?3. Analyze Explain whymost bony fishes producemillions of eggs duringreproduction.________________________4. What is the purpose ofthe lateral line system?________________________________________________________________________Fishes that belong to Chondrichthyes and Osteichthyes havepaired fins.
The fins are fan-shaped membranes. Fins are usedfor balance, swimming, and steering. Fins are attached to andsupported by the endoskeleton. Fins foreshadowed the development of limbs for moving on land and wings for flying.Do fishes have developed sensory systems?All fishes have well-developed sensory systems. Cartilaginousand bony fishes have a lateral line system that helps them senseobjects and changes in their environment. The lateral line systemis a line of fluid-filled canals that runs along the sides of a fish.These canals make it possible for the fish to detect movement andvibrations in the water.Fishes have eyes that allow them to see objects. The eyes alsohelp fishes see contrasts between light and dark in the water.Some fishes see well.
Other fishes that live deep in the oceanwhere there is little or no light have little vision or their eyes donot function at all.Some fishes have a developed sense of smell. These fishes cansmell even small amounts of a chemical in the water. Sharks canfollow a trail of blood for several hundred meters. This abilityhelps sharks find their prey.What are fish scales?Cartilaginous fishes and bony fishes have scales. Fish scalesare thin bony plates formed from the skin.
On some species, thescales are intermittent. This means that the fish body is not completely covered in a continuing pattern of scales. Some specieshave overlapping rows of scales. Scales have various shapes. Theycan be toothlike, shaped like diamonds, shaped like cones, orthey may be round. Shark scales resemble teeth that are found inother vertebrates.366Chapter 30READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.30.1NameDateClassSection30.1Fishes, continuedDo fishes have jaws?The development of jaws in ancestral fishes was animportant event.
Jaws, such as those shown in the figure tothe right, enable a fish to grasp and crush its food. Jawsallowed early fishes to eat a greater variety of organisms.This is one of the reasons that early fishes grew very large.Sharks have jaws. They also have up to 20 rows of teeththat are continually replaced. The teeth of a shark pointbackward. This prevents prey from escaping from theshark’s mouth.JawsGill slitsFish with jawsWhat kinds of skeletons do most fishes have?Most fishes have bony skeletons. They belong to the classOsteichthyes, the bony fishes. The other two classes of fishes haveskeletons made of cartilage, not bone. Bone is the hard, mineralized living tissue that makes up the endoskeleton of most vertebrates.
There are many differences among species of bony fishes.They live in different habitats, eat different organisms, and havedifferent shapes. Their bony skeletons allow them to adapt to avariety of water environments.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Are bony fishes flexible?Bony fishes have a backbone composed of separate, hard segments. These segments are called vertebrae. The evolution of abackbone made of separate vertebrae in the vertebrate skeletonwas important. Vertebrae provide the major support structure ofthe vertebrate skeleton. Because the vertebrae are separate, theanimal is flexible. It can bend its back and its body.
This is especially important for fish movement. When a fish swims, it continually flexes its backbone. Some fish can swim fast because of theirflexible skeletons.5. What is the advantage ofa segmented backbone?________________________________________________________________________What is a swim bladder?A swim bladder is a thin-walled internal sac. It is located justbelow the backbone in most bony fishes. The swim bladder canbe filled with mostly oxygen or nitrogenous gases that diffuse outof a fish’s blood. If a fish has a swim bladder, it can control itsdepth by regulating the amount of gas in the bladder. The gasworks like the gas in a blimp that adjusts the height of the blimpabove the ground.READING ESSENTIALSChapter 30367NameDateClassSection30.1Fishes, continuedSome fishes have a special duct that attaches the swim bladderto the esophagus.
Fishes use this duct to expel gases from theswim bladder. In fishes that do not have this duct, the swim bladder empties when the gases from the bladder diffuse back into thefish’s blood.Diversity of FishesFishes can be tiny. The dwarf goby is less than 1 cm long. Fishesalso can be huge.
The whale shark can grow to 15 m—about thelength of three cars.What are Agnathans?________________________________________________________________________Which fishes are cartilaginous?Sharks, skates, and rays all have skeletons that are composedof cartilage, not bone. They are called cartilaginous fishes. Theybelong to the class Chondrichthyes.
These fishes are similar tothe sharks, skates, and rays that lived more than 100 000 yearsago. Because of this similarity, sharks, skates, and rays are considered living fossils. Sharks are probably the best-known predatorin the ocean.Rays also are predators. They feed on or near the ocean floor.Rays have flat bodies and broad pectoral fins. A pectoral fin beginsnear the fish’s chest.
Rays flap their fins up and down slowly. Thiscreates a gliding motion that rays use as they look for mollusksand crustaceans on the ocean floor. Some species of rays havesharp spines with poison glands on their tails. They use theseglands to protect themselves. Other species of rays have organsthat generate electricity so that the rays can stun or kill theirprey and their predators.Are there any subclasses of bony fishes?There are two subclasses of bony fishes—lobe-finned fishes,including lungfishes, and ray-finned fishes. There are seven living368Chapter 30READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.6.
What is cartilage?Hagfishes and lampreys are members of the superclass Agnathans. The skeleton of an Agnathan is made of cartilage, notbone. Cartilage is a tough, flexible material. Agnathans do nothave jaws. A hagfish has a toothed mouth. It feeds on dead ordying fish. The hagfish can drill a hole into a fish and suck outthe blood and the insides. Lampreys are parasites. Lampreys havesharp teeth and suckerlike mouths. They use their mouths toattack other fishes. They use their teeth to scrape away the fleshfrom their prey.
Then they suck out the blood.NameDateClassSection30.1Fishes, continuedspecies of lobe-finned fishes. Six species of lobe-finned fishes arelungfishes. They have both gills and lungs. The other species isthe coelacanth (SEE luh kanth). Ray-finned fishes include catfish,perch, salmon, and cod.
The fins of these fishes are fan-shapedmembranes. Stiff spines called rays support the fins.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Origins of FishesScientists have found fossils of fishes that existed during the lateCambrian Period, 500 million years ago. At that time, early jawlessfishes called ostracoderms (OHS trah koh durmz) were the mainvertebrates on Earth. Most ostracoderms became extinct at theend of the Devonian Period, about 354 million years ago. Presentday agnathans appear to be descendants of ostracoderms.Ostracoderms swam slowly over the seafloor. They had cartilaginous skeletons and heavy, bony, external armor. Shields ofbone covered their heads and necks. In ancestral fishes, boneformed into plates, or shields, that protected the fishes.
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